Fibrous columnar structure aggregate and pressure-sensitive adhesive member using the aggregate

ABSTRACT

Provided is a fibrous columnar structure aggregate having excellent mechanical properties, a high specific surface area, and excellent pressure-sensitive adhesive property. Provided is a fibrous columnar structure aggregate having excellent heat resistance, a high specific surface area, and excellent pressure-sensitive adhesive property under temperature conditions ranging from room temperature to a high temperature. Provided is a fibrous columnar structure aggregate having a high specific surface area and such pressure-sensitive adhesive property that the adhesive strength for adherends different from each other in surface free energy does not change (aggregate is free of adherend selectivity). Provided is a pressure-sensitive adhesive member using any such fibrous columnar structure aggregate. A fibrous columnar structure aggregate (1) includes fibrous columnar structures having a plurality of diameters, in which: the fibrous columnar structures having a plurality of diameters include fibrous columnar structures each having a length of 500 μm or more; and the mode of the diameter distribution of the fibrous columnar structures having a plurality of diameters is present at 15 nm or less, and the relative frequency of the mode of the diameter distribution is 30% or more.

TECHNICAL FIELD

The present invention relates to a fibrous columnar structure aggregateand an application of the aggregate, and more specifically, to a fibrouscolumnar structure aggregate that brings together excellent mechanicalproperties and a high specific surface area, and a pressure-sensitiveadhesive member using the aggregate.

BACKGROUND ART

Pressure-sensitive adhesives each having various properties have beenused in industrial applications. However, materials for most of theadhesives are viscoelastic bodies each subjected to flexible bulkdesigning. Because of its low modulus, a pressure-sensitive adhesiveformed of a viscoelastic body becomes wet to conform to an adherend,thereby expressing its adhesive strength.

Meanwhile, columnar fibrous structures each having a fine diameter asnovel pressure-sensitive adhesives have been known to show adhesiveproperties. It has been elucidated that the structures each follow thesurface unevenness of an adherend to express its adhesive strength byvirtue of a van der Waals force because the structures each have adiameter of the order of 10⁻⁶ m to 10⁻⁹ m.

A method of using the columnar fibrous structures each having a finediameter in a pressure-sensitive adhesive is, for example, (1) atechnology involving filling a filter having a columnar pore with aresin and removing the filter after the filling to provide thepressure-sensitive adhesive or (2) a technology involving growing thecolumnar fibrous structures each having a fine diameter on an Sisubstrate by chemical vapor deposition (CVD) to provide thepressure-sensitive adhesive (Patent Documents 1 to 3).

However, the above-mentioned technology (1) involves the followingproblem. That is, a filter that can be used is limited, and hence acolumnar fibrous structure that can be produced has an insufficientlength and a low adhesive strength.

In addition, in the above-mentioned technology (2), the adhesivestrength of any one of the columnar fibrous structures is high, andobtains a value equivalent to that of a general-purposepressure-sensitive adhesive in terms of an adhesive strength per unitarea. However, the technology involves the following problem. That is,when evaluation for adhesive strength is performed in an adhesion areaof about 1 cm² in accordance with an adhesion evaluation method for apressure-sensitive adhesive which has been generally performed (PatentDocument 3), the shear adhesive strength of the columnar fibrousstructures is low, and is weak as compared with that of a conventionalgeneral-purpose pressure-sensitive adhesive.

In addition, properties requested of pressure-sensitive adhesives varydepending on applications. Of those, heat resistance is needed for apressure-sensitive adhesive to be used under a high-temperaturecondition. However, pressure-sensitive adhesives using an acrylic resin,a rubber-based resin, a styrene-butadiene copolymer-based resin, and thelike as raw materials serving as general-purpose pressure-sensitiveadhesives that have been generally used each involve the followingproblem. That is, the pressure-sensitive adhesives decompose attemperatures equal to or more than 200° C. because those resins eachhave a low decomposition temperature. In addition, even apressure-sensitive adhesive using a raw material except such resins asdescribed above involves a large change in modulus under ahigh-temperature condition as compared with its modulus at roomtemperature. Accordingly, such a problem that the adhesive strength ofthe pressure-sensitive adhesive under the condition pales beside that atroom temperature, or a contamination problem due to an adhesive residueor the like arises.

In addition, a pressure-sensitive adhesive to be repeatedly bonded to orpeeled from a plurality of adherends is requested to be free of adherendselectivity. However, the pressure-sensitive adhesives using an acrylicresin, a rubber-based resin, a styrene-butadiene copolymer-based resin,and the like as raw materials serving as general-purposepressure-sensitive adhesives that have been generally used each involvethe following problem. That is, the adhesive strength of any such resindepends on the surface free energy of an adherend, and hence thepressure-sensitive adhesives each show adhesive strengths largelydifferent from each other for adherends largely different from eachother in surface free energy.

-   Patent Document 1: U.S. Pat. No. 6,737,160 A-   Patent Document 2: US 2004/0071870 A1-   Patent Document 3: US 2006/0068195 A1

DISCLOSURE OF THE INVENTION Problems to be solved by the Invention

An object of the present invention is to provide a fibrous columnarstructure aggregate having excellent mechanical properties, a highspecific surface area, and excellent pressure-sensitive adhesiveproperty. Another object of the present invention is to provide afibrous columnar structure aggregate having excellent heat resistance, ahigh specific surface area, and excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature. Another object of the present invention is toprovide a fibrous columnar structure aggregate having a high specificsurface area and such pressure-sensitive adhesive property than itsadhesive strength for adherends different from each other in surfacefree energy does not change (the aggregate is free of adherendselectivity). Another object of the present invention is to provide apressure-sensitive adhesive member using any such fibrous columnarstructure aggregate.

Means for Solving the Problems

A fibrous columnar structure aggregate (1) of the present inventionincludes fibrous columnar structures having a plurality of diameters, inwhich:

the fibrous columnar structures having a plurality of diameters includefibrous columnar structures each having a length of 500 μm or more; and

the mode of the diameter distribution of the fibrous columnar structureshaving a plurality of diameters is present at 15 nm or less, and therelative frequency of the mode of the diameter distribution is 30% ormore.

In a preferred embodiment, the above-mentioned fibrous columnarstructures having a plurality of diameters are aligned in a lengthwisedirection.

In a preferred embodiment, a shear adhesive strength for a glass surfaceat room temperature is 15 N/cm² or more.

In a preferred embodiment, the fibrous columnar structure aggregate (1)of the present invention further includes a base material to which oneend of each of the above-mentioned fibrous columnar structures is fixed.

According to another aspect of the present invention, there is provideda fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate.

The fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which:

the fibrous columnar structures are carbon nanotubes, and the carbonnanotubes are carbon nanotubes each having a plurality of walls;

the carbon nanotubes each having a plurality of walls include carbonnanotubes each having a length of 500 μm or more; and

the mode of the wall number distribution of the carbon nanotubes eachhaving a plurality of walls is present within the wall number range of10 or less, and the relative frequency of the mode is 30% or more.

In a preferred embodiment, the above-mentioned carbon nanotubes eachhaving a plurality of walls are aligned in a lengthwise direction.

In a preferred embodiment, the above-mentioned node of the wall numberdistribution is present within the wall number range of 6 or less.

In a preferred embodiment, a shear adhesive strength for a glass surfaceat room temperature is 15 N/cm² or more.

In a preferred embodiment, the fibrous columnar structure aggregate (2)of the present invention further includes a base material to which oneend of each of the above-mentioned carbon nanotubes is fixed.

According to still another aspect of the present invention, there isprovided a fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate.

The fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which:

the fibrous columnar structures are carbon nanotubes, and the carbonnanotubes are carbon nanotubes each having a plurality of walls;

the carbon nanotubes each having a plurality of walls include carbonnanotubes each having a length of 500 μm or more;

the mode of the wall number distribution of the carbon nanotubes eachhaving a plurality of walls is present within the wall number range of10 or less, and the relative frequency of the mode is 30% or more; and

a shear adhesive strength for a glass surface under a 250° C. atmosphereis 0.8 to 1.2 times as high as a shear adhesive strength for the glasssurface at room temperature.

In a preferred embodiment, the above-mentioned carbon nanotubes eachhaving a plurality of walls are aligned in a lengthwise direction.

In a preferred embodiment, the above-mentioned mode of the wall numberdistribution is present within the wall number range of 6 or less.

In a preferred embodiment, the shear adhesive strength for the glasssurface at room temperature is 15 N/cm² or more.

In a preferred embodiment, the fibrous columnar structure aggregate (3)of the present invention further includes a base material to which oneend of each of the above-mentioned carbon nanotubes is fixed.

According to still another aspect of the present invention, there isprovided a fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate.

The fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which:

the fibrous columnar structures are carbon nanotubes, and the carbonnanotubes are carbon nanotubes each having a plurality of walls;

the carbon nanotubes each having a plurality of walls include carbonnanotubes each having a length of 500 μm or more;

the mode of the wall number distribution of the carbon nanotubes eachhaving a plurality of walls is present within the wall number range of10 or less, and the relative frequency of the mode is 30% or more; and

when a shear adhesive strength at room temperature for an adherendhaving a surface free energy a is represented by A and a shear adhesivestrength at room temperature for an adherend having a surface freeenergy b differing from the surface free energy a by 25 mJ/m² or more isrepresented by B (provided that a>b), a value for a ratio B/A is 0.8 to1.2.

In a preferred embodiment, the above-mentioned carbon nanotubes eachhaving a plurality of walls are aligned in a lengthwise direction.

In a preferred embodiment, the above-mentioned mode of the wall numberdistribution is present within the wall number range of 6 or less.

In a preferred embodiment, a shear adhesive strength for a glass surfaceat room temperature is 15 N/cm² or more.

In a preferred embodiment, the fibrous columnar structure aggregate (4)of the present invention further includes a base material to which oneend of each of the above-mentioned carbon nanotubes is fixed.

According to still another aspect of the present invention, there isprovided a pressure-sensitive adhesive member. The pressure-sensitiveadhesive member of the present invention uses the fibrous columnarstructure aggregate of the present invention.

Effects of the Invention

According to the present invention, there can be provided a fibrouscolumnar structure aggregate having excellent mechanical properties, ahigh specific surface area, and excellent pressure-sensitive adhesiveproperty. In addition, there can be provided a fibrous columnarstructure aggregate having excellent heat resistance, a high specificsurface area, and excellent pressure-sensitive adhesive properties undertemperature conditions ranging from room temperature to a hightemperature. In addition, there can be provided a fibrous columnarstructure aggregate having a high specific surface area and suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity). Further, therecan be provided a pressure-sensitive adhesive member using any suchfibrous columnar structure aggregate. In addition, the fibrous columnarstructure aggregate of the present invention is excellent inheat-resistant retaining strength. For example, even after the aggregatehas been crimped onto a slide glass and placed under a high temperatureof, say, 350° C. for 2 hours, the aggregate hardly shifts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a fibrous columnar structureaggregate in a preferred embodiment of the present invention.

FIG. 2 is a schematic sectional view of a carbon nanotubeaggregate-producing apparatus in a preferred embodiment of the presentinvention.

FIG. 3 is a view illustrating the wall number distribution of a carbonnanotube aggregate (1) obtained in Example 1.

FIG. 4 is a view illustrating the wall number distribution of a carbonnanotube aggregate (2) obtained in Example 2.

FIG. 5 is a view illustrating the wall number distribution of a carbonnanotube aggregate (3) obtained in Example 3.

FIG. 6 is a view illustrating the wall number distribution of a carbonnanotube aggregate (C1) obtained in Comparative Example

FIG. 7 is a view illustrating the wall number distribution of a carbonnanotube aggregate (C2) obtained in Comparative Example 2.

FIG. 8 is a view illustrating the wall number distribution of a carbonnanotube aggregate (5) obtained in Example 5.

DESCRIPTION OF SYMBOLS

-   10 fibrous columnar structure aggregate-   1 base material-   2 fibrous columnar structure

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates a schematic sectional view of a fibrous columnarstructure aggregate in a preferred embodiment of the present invention(the view is not precisely illustrated to scale in order that eachconstituent portion may be clearly illustrated). A fibrous columnarstructure aggregate 10 includes a base material 1 and fibrous columnarstructures 2. One end 2 a of each of the fibrous columnar structures isfixed to the base material 1. The fibrous columnar structures 2 arealigned in a lengthwise direction L. The fibrous columnar structures 2are preferably aligned in a direction substantially perpendicular to thebase material 1. Even when the fibrous columnar structure aggregate doesnot include any base material unlike the illustrated example, thefibrous columnar structures can exist as an aggregate by virtue of amutual van der Waals force. Accordingly, the fibrous columnar structureaggregate of the present invention may be an aggregate that does notinclude any base material.

[Fibrous columnar structure aggregate (1)]

A fibrous columnar structure aggregate (1) of the present inventionincludes fibrous columnar structures having a plurality of diameters, inwhich: the fibrous columnar structures having a plurality of diametersinclude fibrous columnar structures each having a length of 500 μm ormore; and the mode of the diameter distribution of the fibrous columnarstructures having a plurality of diameters is present at 15 nm or less,and the relative frequency of the mode of the diameter distribution is30% or more.

Any appropriate material can be adopted as a material for each of theabove-mentioned fibrous columnar structures. Examples of the materialinclude: metals such as aluminum and iron; inorganic materials such assilicon; carbon materials such as a carbon nanofiber and a carbonnanotube; and high-modulus resins such as an engineering plastic and asuper engineering plastic. Specific examples of the resins include apolyimide, a polyethylene, a polypropylene, a polyethyleneterephthalate, an acetylcellulose, a polycarbonate, and a polyamide. Anyappropriate physical property can be adopted as each of the variousphysical properties of any such resin such as a molecular weight to suchan extent that an object of the present invention can be achieved.

The distribution width of the diameter distribution of the fibrouscolumnar structures is preferably 9 nm or less, more preferably 1 to 9nm, still more preferably 2 to 8 nm, or particularly preferably 3 to 8nm.

The “distribution width” of the diameter distribution of the fibrouscolumnar structures described above refers to a difference between themaximum and minimum of the diameters of the fibrous columnar structures.In the present invention, the fibrous columnar structures can bringtogether excellent mechanical properties and a high specific surfacearea, and furthermore, the fibrous columnar structures can be a fibrouscolumnar structure aggregate showing excellent pressure-sensitiveadhesive property when the distribution width of the diameterdistribution of the fibrous columnar structures falls within theabove-mentioned range. It should be noted that the diameters anddiameter distribution of the fibrous columnar structures in the presentinvention have only to be measured with any appropriate apparatus. Themeasurement is preferably performed with a scanning electron microscope(SEM) or a transmission electron microscope (TEM). For example, at leastten, or preferably twenty or more, fibrous columnar structures out ofthe fibrous columnar structure aggregate have only to be evaluated fortheir diameters and diameter distribution by measurement with the SEM orTEM.

The maximum of the diameters of the fibrous columnar structuresdescribed above is preferably 1 to 20 nm, more preferably 2 to 15 nm, orstill more preferably 3 to 10 nm. The minimum of the diameters of thefibrous columnar structures described above is preferably to 10 nm, ormore preferably 1 to 5 nm. In the present invention, the fibrouscolumnar structures can bring together additionally excellent mechanicalproperties and a high specific surface area, and furthermore, thefibrous columnar structures can be a fibrous columnar structureaggregate showing additionally excellent pressure-sensitive adhesiveproperty when the maximum and minimum of the diameters of the fibrouscolumnar structures fall within the above-mentioned ranges.

The relative frequency of the mode of the diameter distributiondescribed above is 30% or more, preferably 30 to 100%, more preferably30 to 90%, still mare preferably 30 to 80%, or particularly preferably30 to 70%. In the present invention, the fibrous columnar structures canbring together excellent mechanical properties and a high specificsurface area, and furthermore, the fibrous columnar structures can be afibrous columnar structure aggregate showing excellentpressure-sensitive adhesive property when the relative frequency of themode of the diameter distribution falls within the above-mentionedrange.

The mode of the diameter distribution described above is present withinthe diameter range of preferably 5 nm to 15 nm, more preferably 5 nm to13 nm, or still more preferably 5 nm to 11 nm. In the present invention,the fibrous columnar structures can bring together excellent mechanicalproperties and a high specific surface area, and furthermore, thefibrous columnar structures can be a fibrous columnar structureaggregate showing excellent pressure-sensitive adhesive property whenthe mode of the diameter distribution falls within the above-mentionedrange.

With regard to the shape of each of the above-mentioned fibrous columnarstructures, the lateral section of the structure has only to have anyappropriate shape. The lateral section is of, for example, asubstantially circular shape, an elliptical shape, or an n-gonal shape(where n represents an integer of 3 or more). In addition, theabove-mentioned fibrous columnar structures may be hollow, or may befilled materials.

The fibrous columnar structures having a plurality of diametersdescribed above include fibrous columnar structures each having a lengthof 500 μm or more. The length of each of the above-mentioned fibrouscolumnar structures is preferably 500 to 10,000 μm, more preferably 500to 1000 μm, or still more preferably 500 to 900 μm. In the presentinvention, the fibrous columnar structures can bring togetheradditionally excellent mechanical properties and a high specific surfacearea, and furthermore, the fibrous columnar structures can be a fibrouscolumnar structure aggregate showing additionally excellentpressure-sensitive adhesive property when the length of each of thefibrous columnar structures falls within the above-mentioned range.

In the fibrous columnar structure aggregate (1) of the presentinvention, the content of fibrous columnar structures each having alength of 500 μm or more in the above-mentioned fibrous columnarstructures is preferably 80 to 100%, more preferably 90 to 100%, stillmore preferably 95 to 100%, particularly preferably 98 to 100%, or mostpreferably substantially 100%. The phrase “substantially 100%” as usedherein refers to a state in which the content is 100% in a detectionlimit in a measuring instrument. In the present invention, theabove-mentioned fibrous columnar structures can bring togetheradditionally excellent mechanical properties and a high specific surfacearea, and furthermore, the fibrous columnar structures can be a fibrouscolumnar structure aggregate showing additionally excellentpressure-sensitive adhesive property when the content of fibrouscolumnar structures each having a length of 500 μm or more in thefibrous columnar structures falls within the above-mentioned range.

The fibrous columnar structure aggregate (1) of the present inventionhas a shear adhesive strength for a glass surface at room temperature ofpreferably 15 N/cm² or more, more preferably 20 to 500 N/cm², still morepreferably 30 to 100 N/cm², particularly preferably 30 to 80 N/cm², orparticularly preferably 35 to 50 N/cm². Here, the term “roomtemperature” as used in the present invention refers to a temperaturecondition of 25° C.

The specific surface area and density of the fibrous columnar structuresdescribed above can each be set to any appropriate value.

In the fibrous columnar structure aggregate (1) of the presentinvention, in the case where the fibrous columnar structures are carbonnanotubes, and the carbon nanotubes are carbon nanotubes each having aplurality of walls, the carbon nanotubes each having a plurality ofwalls preferably include carbon nanotubes each having a length of 500 μmor more, and the mode of the wall number distribution of the carbonnanotubes each having a plurality of walls is preferably present withinthe wall number range of 10 or less, and the relative frequency of themode is 30% or more.

The distribution width of the wall number distribution of the carbonnanotubes each having a plurality of walls described above is morepreferably 9 walls or less, still more preferably 1 to 9 walls,particularly preferably 2 to 8 walls, or most preferably 3 to 8 walls.

The “distribution width” of the wall number distribution of the carbonnanotubes each having the plurality of walls described above refers to adifference between the maximum wall number and minimum wall number ofthe wall numbers of the carbon nanotubes each having the plurality ofwalls. In the present invention, the carbon nanotubes can bring togetherexcellent mechanical properties and a high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive property when thedistribution width of the wall number distribution of the carbonnanotubes each having the plurality of walls falls within theabove-mentioned range. It should be noted that the wall numbers and wallnumber distribution of the carbon nanotubes in the present inventionhave only to be measured with any appropriate apparatus. The measurementis preferably performed with a scanning electron microscope (SEM) or atransmission electron microscope (TEM). For example, at least ten, orpreferably twenty or more, carbon nanotubes out of the carbon nanotubeaggregate have only to be evaluated for their wall numbers and wallnumber distribution by measurement with the SEM or TEM.

The above-mentioned maximum wall number is preferably 1 to 20, morepreferably 2 to 15, or still more preferably 3 to 10. Theabove-mentioned minimum wall number is preferably 1 to 10, or morepreferably 1 to 5. In the present invention, the carbon nanotubes canbring together additionally excellent mechanical properties and a highspecific surface area, and furthermore, the carbon nanotubes can be acarbon nanotube aggregate showing additionally excellentpressure-sensitive adhesive property when the maximum wall number andminimum wall number of the wall numbers of the carbon nanotubes fallwithin the above-mentioned ranges.

The relative frequency of the mode of the wall number distributiondescribed above is more preferably 30 to 100%, still more preferably 30to 90%, particularly preferably 30 to 80%, or most preferably 30 to 70%.In the present invention, the carbon nanotubes can bring togetherexcellent mechanical properties and a high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive property when the relativefrequency of the mode of the wall number distribution falls within theabove-mentioned range.

The mode of the wall number distribution described above is presentwithin the wall number range of preferably 10 or less, more preferably 1to 10, still more preferably 2 to 8, or particularly preferably 2 to 6.In the present invention, the carbon nanotubes can bring togetherexcellent mechanical properties and a high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive property when the mode ofthe wall number distribution falls within the above-mentioned range.

[Fibrous Columnar Structure Aggregate (2): Carbon Nanotube Aggregate]

A fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which: the fibrous columnar structures arecarbon nanotubes, and the carbon nanotubes are carbon nanotubes eachhaving a plurality of walls; the carbon nanotubes each having aplurality of walls include carbon nanotubes each having a length of 500μm or more; and the mode of the wall number distribution of the carbonnanotubes each having a plurality of walls is present within the wallnumber range of 10 or less, and the relative frequency of the mode is30% or more.

The distribution width of the wall number distribution of the carbonnanotubes each having a plurality of walls described above is preferably9 walls or less, more preferably 1 to 9 walls, still more preferably 2to 8 walls, or particularly preferably 3 to 8 walls.

The “distribution width” of the wall number distribution of the carbonnanotubes each having the plurality of walls described above refers to adifference between the maximum wall number and minimum wall number ofthe wall numbers of the carbon nanotubes each having the plurality ofwalls. In the present invention, the carbon nanotubes can bring togetherexcellent mechanical properties and a high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive property when thedistribution width of the wall number distribution of the carbonnanotubes each having the plurality of walls falls within theabove-mentioned range. It should be noted that the wall numbers and wallnumber distribution of the carbon nanotubes in the present inventionhave only to be measured with any appropriate apparatus. The measurementis preferably performed with a scanning electron microscope (SEM) or atransmission electron microscope (TEM). For example, at least ten, orpreferably twenty or more, carbon nanotubes out of the carbon nanotubeaggregate have only to be evaluated for their wall numbers and wallnumber distribution by measurement with the SEM or TEM.

The above-mentioned maximum wall number is preferably 1 to 20, morepreferably 2 to 15, or still more preferably 3 to 10. Theabove-mentioned minimum wall number is preferably 1 to 10, or morepreferably 1 to 5. In the present invention, the carbon nanotubes canbring together additionally excellent mechanical properties and a highspecific surface area, and furthermore, the carbon nanotubes can be acarbon nanotube aggregate showing additionally excellentpressure-sensitive adhesive property when the maximum wall number andminimum wall number of the wall numbers of the carbon nanotubes fallwithin the above-mentioned ranges.

The relative frequency of the mode of the wall number distributiondescribed above is 30% or more, preferably 30 to 100%, more preferably33 to 90%, still more preferably 30 to 80%, or particularly preferably30 to 70%. In the present invention, the carbon nanotubes can bringtogether excellent mechanical properties and a high specific surfacearea, and furthermore, the carbon nanotubes can be a carbon nanotubeaggregate showing excellent pressure-sensitive adhesive property whenthe relative frequency of the mode of the wall number distribution fallswithin the above-mentioned range.

The mode of the wall number distribution described above is presentwithin the wall number range of 10 or less, preferably 1 to 10, morepreferably 2 to 8, or still more preferably 2 to 6. In the presentinvention, the carbon nanotubes can bring together excellent mechanicalproperties and a high specific surface area, and furthermore, the carbonnanotubes can be a carbon nanotube aggregate showing excellentpressure-sensitive adhesive property when the mode of the wall numberdistribution falls within the above-mentioned range.

With regard to the shape of each of the above-mentioned carbonnanotubes, the lateral section of the nanotube has only to have anyappropriate shape. The lateral section is of, for example, asubstantially circular shape, an elliptical shape, or an n-gonal shape(where n represents an integer of 3 or more).

The carbon nanotubes each having a plurality of walls preferably includecarbon nanotubes each having a length of 500 μm or more. The length ofeach of the above-mentioned carbon nanotubes is preferably 500 to 10,000μm, more preferably 500 to 1000 μm, or still more preferably 500 to 900μm. In the present invention, the carbon nanotubes can bring togetheradditionally excellent mechanical properties and a high specific surfacearea, and furthermore, the carbon nanotubes can be a carbon nanotubeaggregate showing additionally excellent pressure-sensitive adhesiveproperty when the length of each of the carbon nanotubes falls withinthe above-mentioned range.

In the fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention, the content of carbon nanotubes eachhaving a length of 500 μm or more in the above-mentioned carbonnanotubes each having the plurality of walls is preferably 80 to 100%,more preferably 90 to 100%, still more preferably 95 to 100%,particularly preferably 98 to 100%, or most preferably substantially100%. The phrase “substantially 100%” as used herein refers to a statein which the content is 100% in a detection limit in a measuringinstrument. In the fibrous columnar structure aggregate (2) as a carbonnanotube aggregate of the present invention, the above-mentioned carbonnanotubes each having the plurality of walls can bring togetheradditionally excellent mechanical properties and a high specific surfacearea, and furthermore, the carbon nanotubes can be a carbon nanotubeaggregate showing additionally excellent pressure-sensitive adhesiveproperty when the content of carbon nanotubes each having a length of500 μm or more in the carbon nanotubes falls within the above-mentionedrange.

The fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention has a shear adhesive strength for aglass surface at room temperature of preferably 15 N/cm² or more, morepreferably 20 to 500 N/cm², still more preferably 30 to 100 N/cm²,particularly preferably 30 to 80 N/cm², or particularly preferably 35 to50 N/cm².

The specific surface area and density of the carbon nanotubes describedabove can each be set to any appropriate value.

In the fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention, a shear adhesive strength for aglass surface under a 250° C. atmosphere is preferably 0.8 to 1.2 times,more preferably 0.85 to 1.15 times, or still more preferably 0.9 to 1.1times as high as a shear adhesive strength for the glass surface at roomtemperature. When the shear adhesive strength for the glass surfaceunder the 250° C. atmosphere is 0.8 to 1.2 times as high as the shearadhesive strength for the glass surface at room temperature, the fibrouscolumnar structure aggregate (2) can be provided with excellent heatresistance, and the fibrous columnar structure aggregate (2) can be acarbon nanotube aggregate showing excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature.

The fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention has a value for a ratio B/A ofpreferably 0.8 to 1.2, more preferably 0.85 to 1.15, or still morepreferably 0.9 to 1.1 where A represents a shear adhesive strength foran adherend having a surface free energy a and B represents a shearadhesive strength for an adherend having a surface free energy bdiffering from the surface free energy a by 25 mJ/m² or more (providedthat a>b). When the value for the ratio B/A is 0.8 to 1.2 where Arepresents the shear adhesive strength for the adherend having thesurface free energy a and B represents the shear adhesive strength forthe adherend having the surface free energy b differing from the surfacefree energy a by 25 mJ/m² or more (provided that a>b), the fibrouscolumnar structure aggregate (2) can be a carbon nanotube aggregatehaving such pressure-sensitive adhesive property that its adhesivestrength for adherends different from each other in surface free energydoes not change (the aggregate is free of adherend selectivity).

When the fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention is peeled from a semiconductor waferafter having been crimped and bonded onto the semiconductor wafer, thenumber of particles each having a size of 0.28 μm or more remaining onthe semiconductor wafer is preferably particles/4-inch wafer or less,more preferably 25 particles/4-inch wafer or less, or still morepreferably 20 particles/4-inch wafer or less. To be additionallyspecific, when the fibrous columnar structure aggregate (2) as a carbonnanotube aggregate of the present invention transferred onto apolypropylene resin is peeled at a 180° peel from a 4-inch semiconductorwafer after having been crimped and attached onto the semiconductorwafer with a 5-kg roller, the number of particles each having a size of0.28 μm or more remaining on the peeled semiconductor wafer ispreferably 30 particles/4-inch wafer or less, more preferably 25particles/4-inch wafer or less, or still more preferably 20particles/4-inch wafer or less. The fibrous columnar structure aggregate(2) as a carbon nanotube aggregate of the present invention is extremelyexcellent in anti-contamination property because the number of particleseach having a size of 0.28 μm or more remaining on a semiconductor waferwhen the aggregate is peeled from the semiconductor wafer after havingbeen crimped and attached onto the semiconductor wafer as describedabove is preferably small as described above.

It should be noted that the 180° peel when evaluation for theabove-mentioned anti-contamination property is performed is measuredwith a tension and compression tester (“TG-1 kN” manufactured by MinebeaCo., Ltd.) in conformity with the adhesion (180° peeling method) of JISC 2107. It should be noted that a test piece is the very fibrouscolumnar structure aggregate (2) as a carbon nanotube aggregate of thepresent invention transferred onto the polypropylene resin (crimped andbonded onto the semiconductor wafer), the crimping is performed byreciprocating the 5-kg roller once, and the measurement is performed ata temperature of 23±2° C., a humidity of 65±5% RH, and a peeling speedof 300 mm/min.

When the fibrous columnar structure aggregate (2) as a carbon nanotubeaggregate of the present invention is fixed to a base material formed ofa polypropylene resin (having a thickness of 30 μm), the value for the180° peel is preferably 1 N/20 mm or less, more preferably 0.001 to 1N/20 mm, still more preferably 0.001 to 0.7 N/20 mm, still further morepreferably 0.001 to 0.5 N/20 mm, or particularly preferably 0.001 to 0.4N/20 mm. The fibrous columnar structure aggregate (2) as a carbonnanotube aggregate of the present invention is extremely excellent inlight-peeling property because the value for the 180° peel when theaggregate is fixed to the base material formed of a polypropylene resin(having a thickness of 30 μm) is preferably small as described above. Inthe case of an ordinary pressure-sensitive adhesive, the value for the180° peel is larger than 1 N/20 mm.

It should be noted that the 180° peel when evaluation for theabove-mentioned light-peeling property is performed is measured with atension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece is the fibrous columnarstructure aggregate (2) as a carbon nanotube aggregate of the presentinvention transferred onto a polypropylene resin having a width of 20mm, a silicon wafer (bare wafer, P type, manufactured by KST) is used asa test panel, the crimping is performed by reciprocating a 2-kg rolleronce, and the measurement is performed at a temperature of 23±2° C., ahumidity of 65±5% RH, and a peeling speed of 300 mm/min.

[Fibrous Columnar Structure Aggregate (3): Carbon Nanotube Aggregate]

A fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which: the fibrous columnar structures arecarbon nanotubes, and the carbon nanotubes are carbon nanotubes eachhaving a plurality of walls; the carbon nanotubes each having aplurality of walls include carbon nanotubes each having a length of 500μm or more; the mode of the wall number distribution of the carbonnanotubes each having a plurality of walls is present within the wallnumber range of 10 or less, and the relative frequency of the mode is30% or more; and a shear adhesive strength for a glass surface under a250° C. atmosphere is 0.8 to 1.2 times as high as a shear adhesivestrength for the glass surface at room temperature.

The distribution width of the wall number distribution of the carbonnanotubes each having a plurality of walls described above is preferably9 walls or less, more preferably 1 to 9 walls, still more preferably 2to 8 walls, or particularly preferably 3 to 8 walls.

The “distribution width” of the wall number distribution of the carbonnanotubes each having the plurality of walls described above refers to adifference between the maximum wall number and minimum wall number ofthe wall numbers of the carbon nanotubes each having the plurality ofwalls. In the present invention, the carbon nanotubes can bring togetheradditionally excellent heat resistance and a high specific surface area,and furthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive properties undertemperature conditions ranging from room temperature to a hightemperature when the distribution width of the wall number distributionof the carbon nanotubes each having the plurality of walls falls withinthe above-mentioned range. It should be noted that the wall numbers andwall number distribution of the carbon nanotubes in the presentinvention have only to be measured with any appropriate apparatus. Themeasurement is preferably performed with a scanning electron microscope(SEM) or a transmission electron microscope (TEM). For example, at leastten, or preferably twenty or more, carbon nanotubes out of the carbonnanotube aggregate have only to be evaluated for their wall numbers andwall number distribution by measurement with the SEM or TEM.

The above-mentioned maximum wall number is preferably 1 to 20, morepreferably 2 to 15, or still more preferably 3 to 10. Theabove-mentioned minimum wall number is preferably 1 to 10, or morepreferably 1 to 5. In the present invention, the carbon nanotubes canbring together further additionally excellent heat resistance and a highspecific surface area, and furthermore, the carbon nanotubes can be acarbon nanotube aggregate showing excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature when the maximum wall number and minimum wall numberof the wall numbers of the carbon nanotubes fall within theabove-mentioned ranges.

The relative frequency of the mode of the wall number distributiondescribed above is 30% or more, preferably 30 to 100%, more preferably30 to 90%, still more preferably 30 to 60%, or particularly preferably30 to 70%. In the present invention, the carbon nanotubes can bringtogether further additionally excellent heat resistance and a highspecific surface area, and furthermore, the carbon nanotubes can be acarbon nanotube aggregate showing excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature when the relative frequency of the mode of the wallnumber distribution falls within the above-mentioned range.

The mode of the wall number distribution described above is presentwithin the wall number range of 10 or less, preferably 1 to 10, morepreferably 2 to 8, or still more preferably 2 to 6. In the presentinvention, the carbon nanotubes can bring together further additionallyexcellent heat resistance and a high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive properties undertemperature conditions ranging from room temperature to a hightemperature when the mode of the wall number distribution falls withinthe above-mentioned range.

With regard to the shape of each of the above-mentioned carbonnanotubes, the lateral section of the nanotube has only to have anyappropriate shape. The lateral section is of, for example, asubstantially circular shape, an elliptical shape, or an n-gonal shape(where n represents an integer of 3 or more).

The carbon nanotubes each having a plurality of walls described abovepreferably include carbon nanotubes each having a length of 500 μm ormore. The length of each of the above-mentioned carbon nanotubes ispreferably 500 to 10,000 μm, more preferably 500 to 1000 μm, or stillmore preferably 500 to 900 μm. In the present invention, the carbonnanotubes can bring together further additionally excellent heatresistance and a high specific surface area, and furthermore, the carbonnanotubes can be a carbon nanotube aggregate showing excellentpressure-sensitive adhesive properties under temperature conditionsranging from room temperature to a high temperature when the length ofeach of the carbon nanotubes falls within the above-mentioned range.

In the fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention, the content of carbon nanotubes eachhaving a length of 500 μm or more in the above-mentioned carbonnanotubes each having the plurality of walls is preferably 80 to 100%,more preferably 90 to 100%, still more preferably 95 to 100%,particularly preferably 98 to 100%, or most preferably substantially100%. The phrase “substantially 100%” as used herein refers to a statein which the content is 100% in a detection limit in a measuringinstrument. In the fibrous columnar structure aggregate (3) as a carbonnanotube aggregate of the present invention, the above-mentioned carbonnanotubes each having the plurality of walls can bring together furtheradditionally excellent heat resistance and a high specific surface area,and furthermore, the carbon nanotubes can be a carbon nanotube aggregateshowing excellent pressure-sensitive adhesive properties undertemperature conditions ranging from room temperature to a hightemperature when the content of carbon nanotubes each having a length of500 μm or more in the carbon nanotubes falls within the above-mentionedrange.

In the fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention, the shear adhesive strength for aglass surface under the 250° C. atmosphere is 0.8 to 1.2 times,preferably 0.85 to 1.15 times, or more preferably 0.9 to 1.1 times ashigh as the shear adhesive strength for the glass surface at roomtemperature. When the shear adhesive strength for the glass surfaceunder the 250° C. atmosphere is 0.8 to 1.2 times as high as the shearadhesive strength for the glass surface at room temperature, the fibrouscolumnar structure aggregate (3) can be provided with excellent heatresistance, and the fibrous columnar structure aggregate (3) can be acarbon nanotube aggregate showing excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature.

The fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention has a shear adhesive strength for aglass surface at room temperature of preferably 15 N/cm² or more, morepreferably 20 to 500 N/cm², still more preferably 30 to 100 N/cm²,particularly preferably 30 to 80 N/cm², or particularly preferably 35 to50 N/cm².

The specific surface area and density of the carbon nanotubes describedabove can each be set to any appropriate value.

The fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention has a value for a ratio B/A ofpreferably 0.8 to 1.2, more preferably 0.85 to 1.15, or still morepreferably 0.9 to 1.1 where A represents a shear adhesive strength foran adherend having a surface free energy a and B represents a shearadhesive strength for an adherend having a surface free energy bdiffering from the surface free energy a by 25 mJ/m² or more (providedthat a>b). When the value for the ratio B/A is 0.8 to 1.2 where Arepresents the shear adhesive strength for the adherend having thesurface free energy a and B represents the shear adhesive strength forthe adherend having the surface free energy b differing from the surfacefree energy a by 25 mJ/m² or more (provided that a>b), the fibrouscolumnar structure aggregate (3) can be a carbon nanotube aggregatehaving such pressure-sensitive adhesive property that its adhesivestrength for adherends different from each other in surface free energydoes not change (the aggregate is free of adherend selectivity).

When the fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention is peeled from a semiconductor waferafter having been crimped and bonded onto the semiconductor wafer, thenumber of particles each having a size of 0.28 μm or more remaining onthe semiconductor wafer is preferably particles/4-inch wafer or less,more preferably 25 particles/4-inch wafer or less, or still morepreferably 20 particles/4-inch wafer or less. To be additionallyspecific, when the fibrous columnar structure aggregate (3) as a carbonnanotube aggregate of the present invention transferred onto apolypropylene resin is peeled at a 180° peel from a 4-inch semiconductorwafer after having been crimped and attached onto the semiconductorwafer with a 5-kg roller, the number of particles each having a size of0.28 μm or more remaining on the peeled semiconductor wafer ispreferably 30 particles/4-inch wafer or less, more preferably 25particles/4-inch wafer or less, or still more preferably 20particles/4-inch wafer or less. The fibrous columnar structure aggregate(3) as a carbon nanotube aggregate of the present invention is extremelyexcellent in anti-contamination property because the number of particleseach having a size of 0.28 μm or more remaining on a semiconductor waferwhen the aggregate is peeled from the semiconductor wafer after havingbeen crimped and attached onto the semiconductor wafer as describedabove is preferably small as described above.

It should be noted that the 180° peel when evaluation for theabove-mentioned anti-contamination property is performed is measuredwith a tension and compression tester (“TG-1 kN” manufactured by MinebeaCo., Ltd.) in conformity with the adhesion (180° peeling method) of JISC 2107. It should be noted that a test piece is the very fibrouscolumnar structure aggregate (3) as a carbon nanotube aggregate of thepresent invention transferred onto the polypropylene resin (crimped andbonded onto the semiconductor wafer), the crimping is performed byreciprocating the 5-kg roller once, and the measurement is performed ata temperature of 23±2° C., a humidity of 65±5% RH, and a peeling speedof 300 mm/min.

When the fibrous columnar structure aggregate (3) as a carbon nanotubeaggregate of the present invention is fixed a base material formed of apolypropylene resin (having a thickness of 30 μm), the value for the180° peel is preferably 1 N/20 mm or less, more preferably 0.001 to 1N/20 mm, still more preferably 0.001 to 0.7 N/20 mm, still further morepreferably 0.001 to 0.5 N/20 mm, or particularly preferably 0.001 to 0.4N/20 mm. The fibrous columnar structure aggregate (3) as a carbonnanotube aggregate of the present invention is extremely excellent inlight-peeling property because the value for the 180° peel when theaggregate is fixed to the base material formed of a polypropylene resin(having a thickness of 30 μm) is preferably small as described above. Inthe case of an ordinary pressure-sensitive adhesive, the value for the180° peel is larger than 1 N/20 mm.

It should be noted that the 180° peel when evaluation for theabove-mentioned light-peeling property is performed is measured with atension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece is the fibrous columnarstructure aggregate (3) as a carbon nanotube aggregate of the presentinvention transferred onto a polypropylene resin having a width of 20mm, a silicon wafer (bare wafer, P type, manufactured by KST) is used asa test panel, the crimping is performed by reciprocating a 2-kg rolleronce, and the measurement is performed at a temperature of 23±2° C., ahumidity of 65±5% RH, and a peeling speed of 300 mm/min.

[Fibrous Columnar Structure Aggregate (4): Carbon Nanotube Aggregate]

A fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention includes a plurality of fibrouscolumnar structures, in which: the fibrous columnar structures arecarbon nanotubes, and the carbon nanotubes are carbon nanotubes eachhaving a plurality of walls; the carbon nanotubes each having aplurality of walls include carbon nanotubes each having a length of 500μm or more; the mode of the wall number distribution of the carbonnanotubes each having a plurality of walls is present within the wallnumber range of 10 or less, and the relative frequency of the node is30% or more; and when a shear adhesive strength at room temperature foran adherend having a surface free energy a is represented by A and ashear adhesive strength at room temperature for an adherend having asurface free energy, b differing from the surface free energy a by 25mJ/m² or more is represented by B (provided that a>b), a value for aratio B/A is 0.8 to 1.2.

The distribution width of the wall number distribution of the carbonnanotubes each having a plurality of walls described above is preferably9 walls or less, more preferably 1 to 9 walls, still more preferably 2to 8 walls, or particularly preferably 3 to 8 walls.

The “distribution width” of the wall number distribution of the carbonnanotubes each having the plurality of walls described above refers to adifference between the maximum wall number and minimum wall number ofthe wall numbers of the carbon nanotubes each having the plurality ofwalls. In the present invention, the carbon nanotubes can be providedwith a further additionally high specific surface area, and the carbonnanotubes can be a carbon nanotube aggregate having suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity) when thedistribution width of the wall number distribution of the carbonnanotubes each having the plurality of walls falls within theabove-mentioned range. It should be noted that the wall numbers and wallnumber distribution of the carbon nanotubes in the present inventionhave only to be measured with any appropriate apparatus. The measurementis preferably performed with a scanning electron microscope (SEM) or atransmission electron microscope (TEM). For example, at least ten, orpreferably twenty or more, carbon nanotubes out of the carbon nanotubeaggregate have only to be evaluated for their wall numbers and wallnumber distribution by measurement with the SEM or TEM.

The above-mentioned maximum wall number is preferably 1 to 20, morepreferably 2 to 15, or still more preferably 3 to 10. Theabove-mentioned minimum wall number is preferably 1 to 10, or morepreferably 1 to 5. In the present invention, the carbon nanotubes can beprovided with a further additionally high specific surface area, and thecarbon nanotubes can be a carbon nanotube aggregate having suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity) when the maximumwall number and minimum wall number of the wall numbers of the carbonnanotubes fall within the above-mentioned ranges.

The relative frequency of the mode of the wall number distributiondescribed above is 30% or more, preferably 30 to 100%, more preferably30 to 90%, still more preferably 30 to 80%, or particularly preferably30 to 70%. In the present invention, the carbon nanotubes can beprovided with a further additionally high specific surface area, andfurthermore, the carbon nanotubes can be a carbon nanotube aggregatehaving such pressure-sensitive adhesive property that its adhesivestrength for adherends different from each other in surface free energydoes not change (the aggregate is free of adherend selectivity) when therelative frequency of the mode of the wall number distribution fallswithin the above-mentioned range.

The mode of the wall number distribution described above is presentwithin the wall number range of 10 or less, preferably 1 to 10, morepreferably 2 to 8, or still more preferably 2 to 6. In the presentinvention, the carbon nanotubes can be provided with a furtheradditionally high specific surface area, and the carbon nanotubes can bea carbon nanotube aggregate having such pressure-sensitive adhesiveproperty that its adhesive strength for adherends different from eachother in surface free energy does not change (the aggregate is free ofadherend selectivity) when the mode of the wall number distributionfalls within the above-mentioned range.

With regard to the shape of each of the above-mentioned carbonnanotubes, the lateral section of the nanotube has only to have anyappropriate shape. The lateral section is of, for example, asubstantially circular shape, an elliptical shape, or an n-gonal shape(where n represents an integer of 3 or more).

The carbon nanotubes each having a plurality of walls described aboveinclude carbon nanotubes each having a length of 500 μm or more. Thelength of each of the above-mentioned carbon nanotubes is preferably 500to 10,000 μm, more preferably 500 to 1000 μm, or still more preferably500 to 900 μm. In the present invention, the carbon nanotubes can beprovided with a further additionally high specific surface area, and thecarbon nanotubes can be a carbon nanotube aggregate having suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity) when the lengthof each of the carbon nanotubes falls within the above-mentioned range.

In the fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention, the content of carbon nanotubes eachhaving a length of 500 μm or more in the above-mentioned carbonnanotubes each having the plurality of walls is preferably 80 to 100%,more preferably 90 to 100%, still more preferably 95 to 100%,particularly preferably 98 to 100%, or most preferably substantially100%. The phrase “substantially 100%” as used herein refers to a statein which the content is 100% in a detection limit in a measuringinstrument. In the fibrous columnar structure aggregate (4) as a carbonnanotube aggregate of the present invention, the above-mentioned carbonnanotubes each having the plurality of walls can be provided with afurther additionally high specific surface area, and the carbonnanotubes can be a carbon nanotube aggregate having suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity) when the contentof carbon nanotubes each having a length of 500 μm or more in the carbonnanotubes falls within the above-mentioned range.

The fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention has a shear adhesive strength for aglass surface at room temperature of preferably 15 N/cm² or more, morepreferably 20 to 500 N/cm², still more preferably 30 to 100 N/cm²,particularly preferably 30 to 83 N/cm², or particularly preferably 35 to50 N/cm².

The fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention has a value for a ratio B/A of 0.8 to1.2, preferably 0.85 to 1.15, or more preferably 0.9 to 1.1 where Arepresents a shear adhesive strength at room temperature for an adherendhaving a surface free energy a and B represents a shear adhesivestrength at room temperature for an adherend having a surface freeenergy b differing from the surface free energy a by 25 mJ/m² or more(provided that a>b). When the value for the ratio B/A is 0.8 to 1.2where A represents the shear adhesive strength at room temperature forthe adherend having the surface free energy a and B represents the shearadhesive strength at room temperature for the adherend having thesurface free energy b differing from the surface free energy a by 25mJ/m² or more (provided that a>b) the fibrous columnar structureaggregate (4) can be a carbon nanotube aggregate having suchpressure-sensitive adhesive property that its adhesive strength foradherends different from each other in surface free energy does notchange (the aggregate is free of adherend selectivity).

The specific surface area and density of the carbon nanotubes describedabove can each be set to any appropriate value.

In the fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention, a shear adhesive strength for aglass surface under a 250° C. atmosphere is preferably 0.9 to 1.2 times,more preferably 0.85 to 1.15 times, or still more preferably 0.9 to 1.1times as high as a shear adhesive strength for the glass surface at roomtemperature. When the shear adhesive strength for the glass surfaceunder the 250° C. atmosphere is 0.8 to 1.2 times as high as the shearadhesive strength for the glass surface at room temperature, the fibrouscolumnar structure aggregate (4) can be provided with excellent heatresistance, and the fibrous columnar structure aggregate (4) can be acarbon nanotube aggregate showing excellent pressure-sensitive adhesiveproperties under temperature conditions ranging from room temperature toa high temperature.

When the fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention is peeled from a semiconductor waferafter having been crimped and bonded onto the semiconductor wafer, thenumber of particles each having a size of 0.28 μm or more remaining onthe semiconductor wafer is preferably particles/4-inch wafer or less,more preferably 25 particles/4-inch wafer or less, or still morepreferably 20 particles/4-inch wafer or less. To be additionallyspecific, when the fibrous columnar structure aggregate (4) as a carbonnanotube aggregate of the present invention transferred onto apolypropylene resin is peeled at a 180° peel from a 4-inch semiconductorwafer after having been crimped and attached onto the semiconductorwafer with a 5-kg roller, the number of particles each having a size of0.28 μm or more remaining on the peeled semiconductor wafer ispreferably 30 particles/4-inch wafer or less, more preferably 25particles/4-inch wafer or less, or still more preferably 20particles/4-inch wafer or less. The fibrous columnar structure aggregate(4) as a carbon nanotube aggregate of the present invention is extremelyexcellent in anti-contamination property because the number of particleseach having a size of 0.28 μm or more remaining on a semiconductor waferwhen the aggregate is peeled from the semiconductor wafer after havingbeen crimped and attached onto the semiconductor wafer as describedabove is preferably small as described above.

It should be noted that the 180° peel when evaluation for theabove-mentioned anti-contamination property is performed is measuredwith a tension and compression tester (“TG-1 kN” manufactured by MinebeaCo., Ltd.) in conformity with the adhesion (180° peeling method) of JISC 2107. It should be noted that a test piece is the very fibrouscolumnar structure aggregate (4) as a carbon nanotube aggregate of thepresent invention transferred onto the polypropylene resin (crimped andbonded onto the semiconductor wafer), the crimping is performed byreciprocating the 5-kg roller once, and the measurement is performed ata temperature of 23±2° C., a humidity of 65±5% RH, and a peeling speedof 300 min/min.

When the fibrous columnar structure aggregate (4) as a carbon nanotubeaggregate of the present invention is fixed to a base material formed ofa polypropylene resin (having a thickness of 30 μm), the value for the180° peel is preferably 1N/20 mm or less, more preferably 0.001 to 1N/20 mm, still more preferably 0.001 to 0.7 N/20 nm, still further morepreferably 0.001 to 0.5 N/20 mm, or particularly preferably 0.001 to 0.4N/20 mm. The fibrous columnar structure aggregate (4) as a carbonnanotube aggregate of the present invention is extremely excellent inlight-peeling property because the value for the 180° peel when theaggregate is fixed to the base material formed of a polypropylene resin(having a thickness of 30 μm) is preferably small as described above. Inthe case of an ordinary pressure-sensitive adhesive, the value for the180° peel is larger than 1 N/20 mm.

It should be noted that the 180° reel when evaluation for theabove-mentioned light-peeling property is performed is measured with atension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test niece is the fibrous columnarstructure aggregate (4) as a carbon nanotube aggregate of the presentinvention transferred onto a polypropylene resin having a width of 20mm, a silicon wafer (bare wafer, P type, manufactured by KST) is used asa test panel, the crimping is performed by reciprocating a 2-kg rolleronce, and the measurement is performed at a temperature of 23±2° C., ahumidity of 65±5% RH, and a peeling speed of 300 mm/min.

[Method of Producing Fibrous Columnar Structure Aggregate]

Any appropriate method can be adopted as a method of producing thefibrous columnar structure aggregate of the present invention. A methodof producing a fibrous columnar structure aggregate as a carbon nanotubeaggregate is described as an example of a preferred embodiment of themethod of producing the fibrous columnar structure aggregate of thepresent invention.

Any appropriate method can be adopted as the method of producing thefibrous columnar structure aggregate as a carbon nanotube aggregate ofthe present invention. The method is, for example, a method of producingan aggregate of carbon nanotubes aligned substantially perpendicularlyfrom a smooth substrate by chemical vapor deposition (CVD) involvingforming a catalyst layer on the substrate and filling a carbon source ina state in which a catalyst is activated with heat, plasma, or the liketo grow the carbon nanotubes. In this case, removing the substrateprovides an aggregate of the carbon nanotubes aligned in a lengthwisedirection.

Any appropriate substrate can be adopted as the above-mentionedsubstrate. The substrate is, for example, a material having smoothnessand high-temperature heat resistance enough to resist the production ofthe carbon nanotubes. Examples of such material include quartz glass,silicon (such as a silicon wafer), and a metal plate made of, forexample, aluminum.

Any appropriate apparatus can be adopted as an apparatus for producingthe fibrous columnar structure aggregate as a carbon nanotube aggregateof the present invention. The apparatus is, for example, a thermal CVDapparatus of a hot wall type formed by surrounding a cylindricalreaction vessel with a resistance heating electric tubular furnace asillustrated in FIG. 2. In this case, for example, a heat-resistantquartz tube is preferably used as the reaction vessel.

Any appropriate catalyst can be used as the catalyst (material for thecatalyst layer) that can be used in the production of the fibrouscolumnar structure aggregate as a carbon nanotube aggregate of thepresent invention. Examples of the catalyst include metal catalysts suchas iron, cobalt, nickel, gold, platinum, silver, and copper.

Upon production of the fibrous columnar structure aggregate as a carbonnanotube aggregate of the present invention, an alumina/hydrophilic filmmay be provided between the substrate and the catalyst layer asrequired.

Any appropriate method can be adopted as a method of producing thealumina/hydrophilic film. For example, the film can be obtained byproducing an SiO₂ film on the substrate, depositing Al from the vapor,and increasing the temperature of Al to 450° C. after the deposition tooxidize Al. According to such production method, Al₂O₃ interacts withthe hydrophilic SiO₂ film, and hence an Al₂O₃ surface different fromthat obtained by directly depositing Al₂O₃ from the vapor in particlediameter is formed. When Al is deposited from the vapor, and then itstemperature is increased to 450° C. so that Al may be oxidized withoutthe production of any hydrophilic film on the substrate, it may bedifficult to form the Al₂O₃ surface having a different particlediameter. In addition, when the hydrophilic film is produced on thesubstrate and Al₂O₃ is directly deposited from the vapor, it may also bedifficult to form the Al₂O₃ surface having a different particlediameter.

The catalyst layer that can be used in the production of the fibrouscolumnar structure aggregate as a carbon nanotube aggregate of thepresent invention has a thickness of preferably 0.01 to 20 nm, or morepreferably 0.1 to 10 nm in order that fine particles may be formed. Whenthe thickness of the catalyst layer that can be used in the productionof the fibrous columnar structure aggregate as a carbon nanotubeaggregate of the present invention falls within the above-mentionedrange, the fibrous columnar structures can bring together excellentmechanical properties and a high specific surface area, and furthermore,the fibrous columnar structures can be a fibrous columnar structureaggregate showing excellent pressure-sensitive adhesive property. Anyappropriate method can be adopted as a method of forming the catalystlayer. Examples of the method include a method involving depositing ametal catalyst from the vapor, for example, with an electron beam (EB)or by sputtering and a method involving applying a suspension of metalcatalyst fine particles onto the substrate.

Any appropriate carbon source can be used as the carbon source that canbe used in the production of the fibrous columnar structure aggregate asa carbon nanotube aggregate of the present invention Examples of thecarbon source include: hydrocarbons such as methane, ethylene,acetylene, and benzene; and alcohols such as methanol and ethanol.

Any appropriate temperature can be adopted as a production temperaturein the production of the fibrous columnar structure aggregate as acarbon nanotube aggregate of the present invention. For example, thetemperature is preferably 400 to 1000° C., more preferably 500 to 900°C., or still more preferably 600 to 800° C. in order that catalystparticles allowing sufficient expression of an effect of the presentinvention may be formed.

[Pressure-Sensitive Adhesive Member]

A pressure-sensitive adhesive member of the present invention uses thefibrous columnar structure aggregate of the present invention. Thepressure-sensitive adhesive member of the present invention ispreferably such that the fibrous columnar structure aggregate of thepresent invention is provided with a base material. Specific examples ofthe member include a pressure-sensitive adhesive sheet and apressure-sensitive adhesive film.

Examples of the base material of the pressure-sensitive adhesive memberinclude quartz glass, silicon (such as a silicon wafer), an engineeringplastic, and a super engineering plastic. Specific examples of theengineering plastic and the super engineering plastic include apolyimide, a polyethylene, a polyethylene terephthalate, anacetylcellulose, a polycarbonate, a polypropylene, and a polyamide. Anyappropriate physical property can be adopted as each of various physicalproperties such as a molecular weight to such an extent that an objectof the present invention can be achieved.

The thickness of the base material can be set to any appropriate valuedepending on purposes. In the case of, for example, a silicon substrate,the thickness is preferably 100 to 10,000 μm, more preferably 100 to5000 μm, or still more preferably 100 to 2000 μm. In the case of, forexample, a polypropylene substrate, the thickness is preferably 1 to1000 μm, more preferably 1 to 500 μm, or still more preferably 5 to 100μm.

The surface of the above-mentioned base material may be subjected to aconventional surface treatment, e.g., a chemical or physical treatmentsuch as a chromic acid treatment, exposure to ozone, exposure to aflame, exposure to a high-voltage electric shock, or an ionizingradiation treatment, or a coating treatment with an under coat (such asthe above-mentioned adherent material) in order that adhesiveness withan adjacent layer, retentivity, or the like may be improved.

The above-mentioned base material may be a single layer, or may be amultilayer body.

When the fibrous columnar structure aggregate of the present inventionis fixed to the base material, any appropriate method can be adopted asa method of fixing the aggregate. For example, the substrate used in theproduction of the fibrous columnar structures may be used as it is as abase material. Alternatively, the aggregate may be fixed by providingthe base material with an adhesion layer. Further, when the basematerial is a thermosetting resin, the aggregate has only to be fixed asdescribed below. That is, a thin film is produced in a state before areaction, one end of a carbon nanotube is crimped onto the thin filmlayer, and then a curing treatment is performed. In addition, when thebase material is a thermoplastic resin, a metal, or the like, theaggregate has only to be fixed by crimping one end of each fibrouscolumnar structure in a state in which the base material is molten, andcooling the resultant to room temperature.

EXAMPLES

Hereinafter, the present invention is described with reference toexamples. However, the present invention is not limited to theseexamples. It should be noted that evaluation for the diameters anddiameter distribution of fibrous columnar structures in a fibrouscolumnar structure aggregate, evaluation for the wall numbers and wallnumber distribution of the fibrous columnar structures in the fibrouscolumnar structure aggregate, the measurement of the shear adhesivestrength of the fibrous columnar structure aggregate, and evaluation forthe surface free energy of an adherend were performed by the followingmethods.

<Evaluation for Diameters and Diameter Distribution of Fibrous ColumnarStructures in Fibrous Columnar Structure Aggregate>

The diameters and diameter distribution of the fibrous columnarstructures in the fibrous columnar structure aggregate of the presentinvention were measured with a scanning electron microscope (SEM) and/ora transmission electron microscope (TEM). At least ten, or preferablytwenty or more, fibrous columnar structures out of the resultant fibrouscolumnar structure aggregate were observed with the SEM and/or the TEM,the diameters of the respective fibrous columnar structures wereexamined, and a diameter distribution was created.

<Evaluation for Wall Numbers and Wall Number Distribution of FibrousColumnar Structures in Fibrous Columnar Structure Aggregate>

The wall numbers and wall number distribution of the fibrous columnarstructures in the fibrous columnar structure aggregate of the presentinvention were measured with a scanning electron microscope (SEM) and/ora transmission electron microscope (TEM). At least ten, or preferablytwenty or more, fibrous columnar structures out of the resultant fibrouscolumnar structure aggregate were observed with the SEM and/or the TEM,the wall numbers of the respective fibrous columnar structures wereexamined, and a wall number distribution was created.

<Measurement Method (A) for Shear Adhesive Strength of Fibrous ColumnarStructure Aggregate>

A fibrous columnar structure aggregate with a base material cut out soas to have a unit area of 1 cm² was mounted on a glass (MATSUNAMI slideglass 27 mm×56 mm) so that its tip might contact the glass. Then, thetips of the fibrous columnar structures were crimped onto the glass byreciprocating a 5-kg roller once. After that, the resultant was left tostand for 30 minutes. A shearing test was performed with a tensiletester (Instro Tensil Tester) at a tension speed of 50 mm/min at 25° C.or 250° C., and the resultant peak was defined as a shear adhesivestrength.

<Measurement Method (B) for Shear Adhesive Strength of Fibrous Columnarstructure aggregate>

A carbon nanotube aggregate with a base material cut out so as to have aunit area of 1 cm² was mounted on a glass (MATSUNAMI slide glass 27mm×56 mm, surface free energy=64. 4 mJ/m²) and PP plate (manufactured byShin-kobe Electric Machinery Co., Ltd., KOBE POLYSHEET PP-N-AN, surfacefree energy=29.8 mJ/m²) so that its tip might contact the glass and thePP plate, respectively. Then, the tips of the carbon nanotube aggregatewere crimped onto the glass by reciprocating a 5-kg roller once. Afterthat, the resultant was left to stand for 30 minutes. A shearing testwas performed with a tensile tester (Instro Tensil Tester) at a tensionspeed of 50 mm/min at 25° C., and the resultant peak was defined as ashear adhesive strength.

<Evaluation for Surface Free Energy of Adherends

Three kinds of liquids (water, glycerin, and methylene iodide) were eachdropped onto the surface of an adherend. After that, a contact angle at100 ms was measured, and the surface free energy was determined with thevalue by the following method.

Method of calculating surface free energy:

γ_(L)(1+cos θ)=2(γ_(L) ^(d)·γ_(s) ^(d))^(1/2)+2(γ_(L) ^(p)·γ_(s)^(p))^(1/2)  (1)

γ_(L): the surface free energy of a liquid used in the contact anglemeasurement

γ_(L) ^(d): the dispersion component of the surface free energy of theliquid

γ_(L) ^(p): the polar component of the surface free energy of the liquid

γ_(s): the surface free energy of a solid to be determined

γ_(s) ^(d): the dispersion component of the surface free energy of thesolid

γ_(s) ^(p): the polar component of the surface free energy of the solid

The equation (1) was transformed into a linear function of (γ_(L)^(p)/γ_(L) ^(d))^(1/2) and γ_(L)(1+cos θ)/2(γ_(L) ^(d))^(1/2).

γ_(L)(1+cos θ)/2(γ_(L) ^(d))^(1/2)=(γ_(s) ^(p))^(1/2)(γ_(L) ^(p)/γ_(L)^(d))^(1/2)+(γ_(s) ^(d))^(1/2)  (2)

In the equation (2), γ_(s) ^(d) was determined by squaring the“gradient” and γ_(s) ^(p) was determined by squaring the “intercept”,and the surface free energy was calculated from the equation“γ_(s)=γ_(s) ^(d)+γ_(s) ^(p).”

Example 1 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 1 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 30 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (1) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (1) eachhad a length of 589 μm.

FIG. 3 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (1). As illustrated in FIG.3, a mode was present at 2 walls, and had a relative frequency of 69%.

In addition, a mode of the diameter distribution of the carbon nanotubeaggregate (1) and the relative frequency of the mode were also measured.

Table 1 summarizes the result

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (1) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (1) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (1) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 15.3 N/cm².

Table 1 summarizes the result.

Example 2

A carbon nanotube aggregate (2) was produced in the same manner as inExample 1 except that an Fe thin film (having a thickness of 2 nm) wasdeposited from the vapor onto the Al₂O₃ film with a sputtering apparatus(manufactured by ULVAC, Inc., RFS-200).

The carbon nanotubes provided for the carbon nanotube aggregate (2) eachhad a length of 637 μm.

FIG. 4 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (2). As illustrated in FIG.4, a mode was present at 3 walls, and had a relative frequency of 50%.

In addition, a mode of the diameter distribution of the carbon nanotubeaggregate (2) and the relative frequency of the mode were also measured.

The carbon nanotube aggregate (2) with a base material was obtained inthe same manner as in Example 1.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (2) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 20.7 N/cm².

Table 1 summarizes the results.

Example 3

A carbon nanotube aggregate (3) was produced in the same manner as inExample 1 except that an Fe thin film (having a thickness of 0.83 nm)was deposited from the vapor onto the Al₂O₃ film with a sputteringapparatus (manufactured by ULVAC, Inc., RFS-200).

The carbon nanotubes provided for the carbon nanotube aggregate (3) eachhad a length of 520 μm.

FIG. 5 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (3). As illustrated in FIG.5, modes were present at 4 walls and 6 walls, and had a relativefrequency of 30% and 30%, respectively.

In addition, a mode of the diameter distribution of the carbon nanotubeaggregate (3) and the relative frequency of the mode were also measured.

The carbon nanotube aggregate (3) with a base material was obtained inthe same manner as in Example 1.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (3) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 25.8 N/cm².

Table 1 summarizes the results.

Comparative Example 1

A carbon nanotube aggregate (C1) was produced in the same manner as inExample 1 except that a mixed gas of helium, hydrogen, and ethylene(105/80/15 sccm, moisture content: 350 ppm) was filled into the quartztube, and then the tube was left to stand for 10 minutes so that carbonnanotubes might be grown on the substrate.

The carbon nanotubes provided for the carbon nanotube aggregate (C1)each had a length of 290 μm.

FIG. 6 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (C1). As illustrated in FIG.6, a mode was present at 2 walls, and had a relative frequency of 66%.

In addition, a mode of the diameter distribution of the carbon nanotubeaggregate (C1) and the relative frequency of the mode were alsomeasured.

The carbon nanotube aggregate (C1) with a base material was obtained inthe same manner as in Example 1.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (C1) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 5.0 N/cm²

Table 1 summarizes the results.

Comparative Example 2 Production of Carbon Nanotube Aggregate

An Fe thin film (having a thickness of 4 nm) was deposited from thevapor onto a silicon substrate (manufactured by ELECTRONICS ANDMATERIALS CORPORATION LIMITED and having a thickness of 525 μm) with asputtering apparatus (manufactured by ULVAC, Inc., RFS-200). Thus, acatalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. Helium (260 sccm) wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 700° C. with an electric tubular furnace in 30 minutes in a stepwisefashion, and was then stabilized at 700° C. After the tube had been leftto stand at 700° C. for 10 minutes, a mixed gas of helium and acetylene(245/15 sccm) was filled into the tube while the temperature wasretained. Then, the tube was left to stand for 30 minutes so that carbonnanotubes might be grown on the substrate. Thus, a carbon nanotubeaggregate (C2) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (C2)each had a length of 506 μm.

FIG. 7 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (C2). As illustrated in FIG.7, a mode was present at 16 walls, and had a relative frequency of 33%.

In addition, a mode of the diameter distribution of the carbon nanotubeaggregate (C2) and the relative frequency of the mode were alsomeasured.

Table 1 summarizes the results.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (C2) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (C2) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (C2) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 1.2 N/cm²

Table 1 summarizes the result.

TABLE 1 Mode of diameter Mode of wall number Length of distributiondistribution carbon nanotube Shear adhesive (relative (relativeaggregate strength frequency) frequency) (μm) (N/cm²) Example 1  5 nm(85.7%) 2 walls (69%) 589 15.3 Example 2 10 nm (36.4%) 3 walls (50%) 63720.7 Example 3 11 nm (40%)  4 walls (30%) 520 25.8 6 walls (30%)Comparative 5 nm (85%)  2 walls (66%) 290 5.0 Example 1 Comparative 20nm (37.5%) 16 walls (33%)  506 1.2 Example 2

Example 4 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, an Fe thin film(having a thickness of 0.35 nm) was further deposited from the vaporonto the Al thin film with a sputtering apparatus (manufactured byULVAC, Inc., RFS-200).

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/00/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 30 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (4) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (4) eachhad a length of 770 μm.

In the carbon nanotube aggregate (4), the wall number distribution waspresent at 1 walls and 2 walls, and a mode was present at 1 walls, andhad a relative frequency of 63.2%.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (4) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (4) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (4) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 15.1 N/cm².

Example 5 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 1 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 ram. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 380 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 60 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (5) was obtained.

The carbon nanotubes provided for carbon nanotube aggregate (5) each hada length of 830 μm.

FIG. 8 illustrates the wall number distribution of the carbon nanotubesprovided for the carbon nanotube aggregate (5). As illustrated in FIG.8, a mode was present at 2 walls, and had a relative frequency of 69%.

Table 2 summarizes the results.

(Measurement of Shear Adhesive Strength)

The carbon nanotubes (single-walled carbon nanotubes) provided for theabove-mentioned carbon nanotube aggregate (5) were taken out with aspatula, and one end of each of the carbon nanotubes was crimped onto aglass (MATSUNAMI slide glass 27 mm×56 mm). Thus, the carbon nanotubeaggregate (5) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (5) with the base material as a sample (measurement method(A)). The shear adhesive strengths were 16.4 N/cm² at room temperatureand 19.1 N/cm² at 250° C.

Table 2 summarizes the result.

Comparative Example 3

Shear adhesive strengths were each measured in the same manner as inExample 5 by using a general-purpose pressure-sensitive adhesive(manufactured by Nitto Denko Corporation, 31B) as a sample (measurementmethod (A)). The shear adhesive strengths were 65.3 N/cm² at roomtemperature and 33.2 N/cm² at 250° C.

Table 2 summarizes the results.

TABLE 2 Mode of wall Length of Shear adhesive strength Distributionnumber carbon (N/cm²) width of wall distribution nanotube Room number(relative aggregate temperature 250° C. distribution frequency) (μm) (A)(B) B/A Example 5 4 walls 2 walls 890 16.4 19.1 1.15 (2~5 walls) (69%)Comparative — — — 65.3 33.2 0.51 Example 3

In Examples 5, the shear adhesive strength for the glass surface under a250° C. atmosphere was 0.8 to 1.2 times as high as the shear adhesivestrength for the glass surface at room temperature. In contrast, in thecase where a general-purpose pressure-sensitive adhesive was used likeComparative Example 3, the shear adhesive strength for the glass surfaceunder a 250° C. atmosphere was less than 0.8 time as high as the shearadhesive strength for the glass surface at room temperature, and hence asignificant reduction in adhesive strength was observed.

Example 6

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the carbon nanotube aggregate (5) obtained in Example 5 was crimpedonto the molten polypropylene resin. After that, the carbon nanotubeswere fixed by cooling the resultant to room temperature. Thus, a carbonnanotube aggregate (5′) with a base material was obtained.

Shear adhesive strengths were measured by using the carbon nanotubeaggregate (5′) with the base material as a sample (measurement method(B)). The shear adhesive strengths were as described below. A shearadhesive strength A for an adherend (glass) having a surface free energyof 64.4 mJ/m² was 15.5 N/cm² and a shear adhesive strength B for anadherend (PP plate) having a surface free energy of 29.8 mJ/m² was 15.7N/cm².

Table 3 summarizes the results.

Comparative Example 4

Shear adhesive strengths were measured by using the general-purposepressure-sensitive adhesive used in Comparative Example 3 (manufacturedby Nitta Denko Corporation, 31B) as a sample (measurement method (B)).The shear adhesive strengths were as described below. A shear adhesivestrength A for an adherend (glass) having a surface free energy of 64.4mJ/m² was 65.0 N/cm² and a shear adhesive strength B for an adherend (PPplate) having a surface free energy of 29.8 mJ/m² was 37.0 N/cm².

Table 3 summarizes the results.

TABLE 3 Mode of wall number Length of Shear adhesive Distributiondistri- carbon strength (N/cm²) width of wall bution nano tube PP number(relative aggregate Glass plate distribution frequency) (μm) (A) (B) B/AExample 6 4 walls 2 walls 890 15.5 15.7 0.95 (2~5 walls) (69%)Comparative — — — 65.0 37.0 0.57 Example 4

In Example 6, when the shear adhesive strength at room temperature forthe adherend (glass) having a surface free energy of 64.4 mJ/m² wasrepresented by A and the shear adhesive strength at room temperature forthe adherend (PP plate) having a surface free energy of 29.8 mJ/m² wasrepresented by B, a value for a ratio B/A was 0.8 to 1.2. In contrast,in the case where a general-purpose pressure-sensitive adhesive was usedlike Comparative Example 4, when the shear adhesive strength at roomtemperature for the adherend (glass) having a surface free energy of64.4 mJ/m² was represented by A and the shear adhesive strength at roomtemperature for the adherend (PP plate) having a surface free energy of29.8 mJ/m² was represented by B, the value for the ratio B/A was lessthan 0.8, and hence a significant reduction in adhesive strength wasobserved.

Example 7 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 1 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 33 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (7) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (7) eachhad a length of 600 μm.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (7) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (7) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (7) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 15.30 N/cm².

(Evaluation for Anti-Contamination Property)

The carbon nanotube aggregate (7) with the base material was crimped andbonded onto a semiconductor wafer having a diameter of 4 inches and athickness of 500 μm in a class 10 clean room by reciprocating a 5-kgroller once. After a lapse of 1 hour, the aggregate was peeled at a 180°peel. The number of particle contaminants each having a size of 0.28 μmor more remaining on the peeled surface was measured with a lasersurface-inspecting apparatus (LS-5000 manufactured by HitachiElectronics Engineering Co., Ltd.). The number of particles each havinga size of 0.28 μm or more remaining on the peeled semiconductor waferwas 15 particles/4-inch wafer.

It should be noted that the 180° peel in the above-mentioned evaluationfor anti-contamination property was measured with a tension andcompression tester (“TG-1 kN” manufactured by Minebea Co., Ltd.) inconformity with the adhesion (180° peeling method) of JIS C 2107. Itshould be noted that a test piece was the carbon nanotube aggregate (7)with the base material, the crimping was performed by reciprocating the5-kg roller once, and the measurement was performed at a temperature of23±2° C., a humidity of 65±5% RH, and a peeling speed of 300 mm/min.

(Evaluation for Light-Peeling Property)

A 180° peel was measured as evaluation for light-peeling property. The180° peel as the evaluation for light-peeling property was measured witha tension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece was the carbon nanotubeaggregate (7) with the base material having a width of 20 mm, a siliconwafer (bare wafer, P type, manufactured by KST) was used as a testpanel, crimping was performed by reciprocating a 2-kg roller once, andthe measurement was performed at a temperature of 23±2° C., a humidityof 65±5% RH, and a peeling speed of 300 mm/min. As a result of themeasurement, the 180° peel was 0.34 N/20 mm.

Example 8 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JELL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 1 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 50 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (8) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (8) eachhad a length of 780 μm.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hotplate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (8) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (8) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (8) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 17.50 N/cm².

(Evaluation for Anti-Contamination Property)

The carbon nanotube aggregate (8) with the base material was crimped andbonded onto a semiconductor wafer having a diameter of 4 inches and athickness of 500 μm in a class 10 clean room by reciprocating a 5-kgroller once. After a lapse of 1 hour, the aggregate was peeled at a 180°peel. The number of particle contaminants each having a size of 0.28 μmor more remaining on the peeled surface was measured with a lasersurface-inspecting apparatus (LS-5000 manufactured by HitachiElectronics Engineering Co., Ltd.). The number of particles each havinga size of 0.28 μm or more remaining on the peeled semiconductor waferwas 18 particles/4-inch wafer.

It should be noted that the 180° peel in the above-mentioned evaluationfor anti-contamination property was measured with a tension andcompression tester (“TG-1 kN” manufactured by Minebea Co., Ltd.) inconformity with the adhesion (180° peeling method) of JIS C 2107. Itshould be noted that a test piece was the carbon nanotube aggregate (8)with the base material, the crimping was performed by reciprocating the5-kg roller once, and the measurement was performed at a temperature of23±2° C., a humidity of 65±5% RH, and a peeling speed of 300 mm/min.

(Evaluation for Light-Peeling Property)

A 180° peel was measured as evaluation for light-peeling property. The180° peel as the evaluation for light-peeling property was measured witha tension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece was the carbon nanotubeaggregate (8) with the base material having a width of 20 mm, a siliconwafer (bare wafer, P type, manufactured by KST) was used as a testpanel, crimping was performed by reciprocating a 2-kg roller once, andthe measurement was performed at a temperature of 23±2° C., a humidityof 65±5% RH, and a peeling speed of 300 mm/min. As a result of themeasurement, the 180° peel was 0.10 N/20 mm.

Example 9 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 2 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 50 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (9) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (9) eachhad a length of 850 μm.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (9) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (9) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (9) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 20.60 N/cm².

(Evaluation for Anti-Contamination Property)

The carbon nanotube aggregate (9) with the base material was crimped andbonded onto a semiconductor wafer having a diameter of 4 inches and athickness of 500 μm in a class 10 clean room by reciprocating a 5-kgroller once. After a lapse of 1 hour, the aggregate was peeled at a 180°peel. The number of particle contaminants each having a size of 0.28 μmor more remaining on the peeled surface was measured with a lasersurface-inspecting apparatus (LS-5000 manufactured by HitachiElectronics Engineering Co., Ltd.). The number of particles each havinga size of 0.28 μm or more remaining on the peeled semiconductor waferwas 24 particles/4-inch wafer.

It should be noted that the 180° peel in the above-mentioned evaluationfor anti-contamination property was measured with a tension andcompression tester (“TG-1 kN” manufactured by Minebea Co., Ltd.) inconformity with the adhesion (180° peeling method) of JIS C 2107. Itshould be noted that a test piece was the carbon nanotube aggregate (9)with the base material, the crimping was performed by reciprocating the5-kg roller once, and the measurement was performed at a temperature of23±2° C., a humidity of 65±5% RH, and a peeling speed of 300 mm/min.

(Evaluation for Light-Peeling Property)

A 130° peel was measured as evaluation for light-peeling property. The180° peel as the evaluation for light-peeling property was measured witha tension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece was the carbon nanotubeaggregate (9) with the base material having a width of 20 mm, a siliconwafer (bare wafer, P type, manufactured by KST) was used as a testpanel, crimping was performed by reciprocating a 2-kg roller once, andthe measurement was performed at a temperature of 23±2° C., a humidityof 65±5% RH, and a peeling speed of 300 mm/min. As a result of themeasurement, the 180° peel was 0.60 N/20 mm.

Example 10 Production of Carbon Nanotube Aggregate

An Al thin film (having a thickness of 10 nm) was formed on a siliconsubstrate (manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITEDand having a thickness of 525 μm) with a vacuum evaporator (manufacturedby JEOL Ltd., JEE-4X Vacuum Evaporator). After that, the resultant wassubjected to an oxidation treatment at 450° C. for 1 hour. Thus, anAl₂O₃ film was formed on the silicon substrate. An Fe thin film (havinga thickness of 2 nm) was further deposited from the vapor onto the Al₂O₃film with a sputtering apparatus (manufactured by ULVAC, Inc., RFS-200).Thus, a catalyst layer was formed.

Next, the silicon substrate with the catalyst layer was cut and mountedin a quartz tube having a diameter of 30 mm. A mixed gas of helium andhydrogen (120/80 sccm) with its moisture content kept at 350 ppm wasflowed into the quartz tube for 30 minutes so that the air in the tubemight be replaced. After that, the temperature in the tube was increasedto 765° C. with an electric tubular furnace in 35 minutes in a stepwisefashion, and was then stabilized at 765° C. After the tube had been leftto stand at 765° C. for 10 minutes, a mixed gas of helium, hydrogen, andethylene (105/80/15 sccm, moisture content: 350 ppm) was filled into thetube while the temperature was retained. Then, the tube was left tostand for 40 minutes so that carbon nanotubes might be grown on thesubstrate. Thus, a carbon nanotube aggregate (10) was obtained.

The carbon nanotubes provided for the carbon nanotube aggregate (10)each had a length of 780 μm.

(Measurement of Shear Adhesive Strength)

A polypropylene resin (manufactured by KYOKUYO PULP & PAPER CO., LTD andhaving a thickness of 30 μm) was heated to 200° C. on a hot plate so asto melt. One end (upper end) of each of the carbon nanotubes providedfor the above-mentioned carbon nanotube aggregate (10) was crimped ontothe molten polypropylene resin. After that, the carbon nanotubes werefixed by cooling the resultant to room temperature. Thus, the carbonnanotube aggregate (10) with a base material was obtained.

A shear adhesive strength was measured by using the carbon nanotubeaggregate (10) with the base material as a sample at 25° C. (measurementmethod (A)). The shear adhesive strength was 27.20 N/cm².

(Evaluation for Anti-Contamination Property)

The carbon nanotube aggregate (10) with the base material was crimpedand bonded onto a semiconductor wafer having a diameter of 4 inches anda thickness of 500 μm in a class 10 clean room by reciprocating a 5-kgroller once. After a lapse of 1 hour, the aggregate was peeled at a 180°peel. The number of particle contaminants each having a size of 0.28 μmor more remaining on the peeled surface was measured with a lasersurface-inspecting apparatus (LS-5000 manufactured by HitachiElectronics Engineering Co., Ltd.). The number of particles each havinga size of 0.28 μm or more remaining on the peeled semiconductor waferwas 30 particles/4-inch wafer.

It should be noted that the 180° peel in the above-mentioned evaluationfor anti-contamination property was measured with a tension andcompression tester (“TG-1 kN” manufactured by Minebea Co., Ltd.) inconformity with the adhesion (180° peeling method) of JIS C 2107. Itshould be noted that a test piece was the carbon nanotube aggregate (10)with the base material, the crimping was performed by reciprocating the5-kg roller once, and the measurement was performed at a temperature of23±2° C., a humidity of 65±5% RH, and a peeling speed of 300 mm/min.

(Evaluation for Light-Peeling Property)

A 180° peel was measured as evaluation for light-peeling property. The180° peel as the evaluation for light-peeling property was measured witha tension and compression tester (“TG-1 kN” manufactured by Minebea Co.,Ltd.) in conformity with the adhesion (180° peeling method) of JIS C2107. It should be noted that a test piece was the carbon nanotubeaggregate (10) with the base material having a width of 20 mm, a siliconwafer (bare wafer, P type, manufactured by KST) was used as a testpanel, crimping was performed by reciprocating a 2-kg roller once, andthe measurement was performed at a temperature of 23±2° C., a humidityof 65±5% RH, and a peeling speed of 300 nm/min. As a result of themeasurement, the 180° peel was 0.97 N/20 mm.

INDUSTRIAL APPLICABILITY

The fibrous columnar structure aggregate of the present invention can besuitably used as a pressure-sensitive adhesive because the aggregate hasexcellent pressure-sensitive adhesive property. In addition, theaggregate can be used as, for example, a protective sheet at the time ofthe processing of a semiconductor wafer.

1. A fibrous columnar structure aggregate comprising fibrous columnarstructures having a plurality of diameters, wherein: the fibrouscolumnar structures comprise carbon nanotubes; the fibrous columnarstructures having a plurality of diameters include fibrous columnarstructures each having a length of 500 μm or more; and a mode of adiameter distribution of the fibrous columnar structures having aplurality of diameters is present at 15 nm or less, and a relativefrequency of the mode of the diameter distribution is 30% or more.
 2. Afibrous columnar structure aggregate according to claim 1, wherein thefibrous columnar structures having a plurality of diameters are alignedin a lengthwise direction.
 3. A fibrous columnar structure aggregateaccording to claim 1, wherein a shear adhesive strength for a glasssurface at room temperature is 15 N/cm² or more.
 4. A fibrous columnarstructure aggregate according to claim 1, further comprising a basematerial to which one end of each of the fibrous columnar structures isfixed.
 5. A fibrous columnar structure aggregate as a carbon nanotubeaggregate, the fibrous columnar structure aggregate comprising aplurality of fibrous columnar structures, wherein: the fibrous columnarstructures comprise carbon nanotubes, and the carbon nanotubes comprisecarbon nanotubes each having a plurality of walls; the carbon nanotubeseach having a plurality of walls include carbon nanotubes each having alength of 500 μm or more; and a mode of a wall number distribution ofthe carbon nanotubes each having a plurality of walls is present withina wall number range of 10 or less, and a relative frequency of the modeis 30% or more.
 6. A fibrous columnar structure aggregate according toclaim 5, wherein the carbon nanotubes each having a plurality of wallsare aligned in a lengthwise direction.
 7. A carbon nanotube aggregateaccording to claim 5, wherein the mode of the wall number distributionis present within a wall number range of 6 or less.
 8. A fibrouscolumnar structure aggregate according to claim 5, wherein a shearadhesive strength for a glass surface at room temperature is 15 N/cm² ormore.
 9. A fibrous columnar structure aggregate according to claim 5,further comprising a base material to which one end of each of thecarbon nanotubes is fixed.
 10. A fibrous columnar structure aggregate asa carbon nanotube aggregate, the fibrous columnar structure aggregatecomprising a plurality of fibrous columnar structures, wherein: thefibrous columnar structures comprise carbon nanotubes, and the carbonnanotubes comprise carbon nanotubes each having a plurality of walls;the carbon nanotubes each having a plurality of walls include carbonnanotubes each having a length of 500 μm or more; a mode of a wallnumber distribution of the carbon nanotubes each having a plurality ofwalls is present within a wall number range of 10 or less, and arelative frequency of the mode is 30% or more; and a shear adhesivestrength for a glass surface under a 250° C. atmosphere is 0.8 to 1.2times as high as a shear adhesive strength for the glass surface at roomtemperature.
 11. A fibrous columnar structure aggregate according toclaim 10, wherein the carbon nanotubes each having a plurality of wallsare aligned in a lengthwise direction.
 12. A fibrous columnar structureaggregate according to claim 10, wherein the mode of the wall numberdistribution is present within a wall number range of 6 or less.
 13. Afibrous columnar structure aggregate according to claim 10, wherein theshear adhesive strength for the glass surface at room temperature is 15N/cm² or more.
 14. A fibrous columnar structure aggregate according toclaim 10, further comprising a base material to which one end of each ofthe carbon nanotubes is fixed.
 15. A fibrous columnar structureaggregate as a carbon nanotube aggregate, the fibrous columnar structureaggregate comprising a plurality of fibrous columnar structures,wherein: the fibrous columnar structures comprise carbon nanotubes, andthe carbon nanotubes comprise carbon nanotubes each having a pluralityof walls; the carbon nanotubes each having a plurality of walls includecarbon nanotubes each having a length of 500 μm or more; a mode of awall number distribution of the carbon nanotubes each having a pluralityof walls is present within a wall number range of 10 or less, and arelative frequency of the mode is 30% or more; and when a shear adhesivestrength at room temperature for an adherend having a surface freeenergy a is represented by A and a shear adhesive strength at roomtemperature for an adherend having a surface free energy b differingfrom the surface free energy a by 25 mJ/m² or more is represented by Bprovided that a>b, a value for a ratio B/A is 0.8 to 1.2.
 16. A fibrouscolumnar structure aggregate according to claim 15, wherein the carbonnanotubes each having a plurality of walls are aligned in a lengthwisedirection.
 17. A fibrous columnar structure aggregate according to claim15, wherein the mode of the wall number distribution is present within awall number range of 6 or less.
 18. A fibrous columnar structureaggregate according to claim 15, wherein a shear adhesive strength for aglass surface at room temperature is 15 N/cm² or more.
 19. A fibrouscolumnar structure aggregate according to claim 15, further comprising abase material to which one end of each of the carbon nanotubes is fixed.20. A pressure-sensitive adhesive member using the fibrous columnarstructure aggregate according to claim 1.